This invention relates to an apparatus for mixing (blending) textile fibers such as cotton or chemical fibers or the like and is of the type which has a plurality of serially arranged hoppers which are charged with fibers from above by a common pneumatic fiber conveying device. The fiber material is withdrawn from the hoppers at their lower end, for example, by means of delivery rolls cooperating with opening rolls and transported by a common conveyor through a fiber mixing chamber. The conveying air is separated from the fiber tufts and is guided through air outlet openings into an exhaust-air chamber.
In a mixer of conventional structure, the conveying air is guided through perforated plates in the upper part of the chamber into lateral exhaust channels and from there the air is introduced into the mixing chamber underneath the opening rolls at the bottom of the hoppers. The opening rolls advance the fiber material (fiber tufts) into the mixing chamber from which they are drawn away by suction by means of an after-connected condenser having a screen drum and a suction output which is at least 3,600 m.sup.3 /hr. The loose fiber tufts are in a floating state in the mixing chamber as they are withdrawn by suction therefrom. The screen drum has a cylindrical surface on which first a densified fiber lap layer is formed from the loosely adhering fiber tufts, and then the fiber material is fed, as a fiber tuft batt, to an after-connected fiber-processing machine, such as a fiber cleaner. Such an arrangement is complex and expensive; it is a further disadvantage that the separated conveying air which is also used for removing the mixed fiber tufts has a certain dust content.